The present invention relates to multiple circuit card configurations which provide efficient space utilization, electrical continuity between adjacent circuit boards and cooling of the electrical components mounted on the cards for such applications as missile electronics units.
For most applications, the size of the electrical circuit cards on which the electrical components are mounted in an electronics unit is limited by packaging constraints and the like. As a result, multiple circuit boards or cards are employed in close-packed arrangements. One such application is that of guided vehicles, such as missiles or torpedos, wherein the guidance electronics unit is packaged within the relatively narrow tubular configuration of the vehicle body. A number of circuit cards are typically employed to comprise the electronics unit. In conventional arrangements, multiple pin connectors are located on one edge of each circuit card. These connectors are then mated to matching connectors on a "motherboard" which provides a means to electrically couple power and signals between the various cards. For missiles, the motherboard is typically aligned parallel to but offset from the longitudinal axis of the missile, with the circuit cards being arranged perpendicular to the longitudinal axis of the missile. The motherboard is supported by elongated rails extending along the missile sides, and the circuit cards are supported by the connectors and by card guides secured to the rails. A significant disadvantage of this approach is that the number of connector pins is limited by the confined area, and the assembly and testing operations are necessarily complex. The configuration also wastes much of the available space, and the pin connectors required are quite expensive. Moreover, the configuration is not conducive to reliable operation in applications wherein the circuit card arrangement is subjected to high G forces.
The electronics sections of missiles are typically exposed to high G forces, and the circuit cards, connectors and related hardware must be structurally adapted and secured to withstand such forces while providing satisfactory electrical performance. Because the circuitry is typically arranged in a plurality of closely packed boards with relatively high power output, severe heat dissipation requirements are also common.
Two approaches have been used in the past to meet the severe heat dissipation requirements of missile electronics units. Both approaches employ ceramic circuit cards which are difficult to repair and are easily damaged in removal. The first involves an active cooling technique wherein a fluid is circulated through a plate on which the circuit card is mounted. This approach requires a complex cooling system, and conventionally depends upon bonding of frangible ceramic cards to the coolant plate to provide the necessary thermal conductivity. The cooling achieved by this approach is typically not uniform, the bonds do not provide high heat conductivity, and repair is difficult. The second approach is to provide passive cooling to the ceramic cards by bonding them to metallic heat sinks, typically aluminum. This approach also has the drawbacks of non-uniform cooling, low conductivity of the bonds, and difficulty of repair, and in addition is highly weight inefficient.
In conventional guided vehicle or missile configurations, the seeker platform supporting the seeker elements is located at the forward region of the missile, and is separated from the aft missile body by the electronics unit. The boresight of the seeker platform must be properly aligned with the aft missile body to provide accurate missile guidance and control. The alignment is typically achieved by mechanical means, such as shimming the platform as it is secured to the structural rails to achieve a parallel alignment between the platform and a corresponding parallel surface of the aft missile section, while the assembled missile is mounted on a test fixture for optical or RF measurements. The alignment procedure is time consuming and adds significantly to the cost of the missile assembly.
It would therefore represent an advance in the art to provide a circuit board configuration which provides a simple, low cost means of interconnecting multiple cards in an electronics unit without the use of conventional pin connectors, while providing an increased circuit board area.
It would further be advantageous to provide a multiple circuit card configuration which provides a simple and low cost means for cooling the electrical components mounted on the circuit cards.
It would further be advantageous to provide a guided vehicle configuration which substantially eliminates the need for expensive boresighting tests and procedures to align the seeker platform with the aft vehicle body.